IGF-I signaling prevents dehydroepiandrosterone (DHEA)-induced apoptosis in hypothalamic neurons

Intranasal Administration of Proinsulin C-Peptide Enhances the Stimulating Effect of Insulin on Insulin System Activity in the Hypothalamus of Diabetic Rats

In type 1 diabetes mellitus, the levels of insulin and C-peptide decrease at the periphery and in CNS. C-peptide potentiates the regulatory effects of insulin. We studied the effects of single and repeated (over 7 days) individual and combined nasal administration of C-peptide (10 μg/day) and insulin (20 μg/day) on activity of Akt kinase and kinase-3β-glycogen synthase (GSK3β), the components of 3-phosphoinositide pathway, in the hypothalamus of intact rats and rats with mild streptozotocin-induced type 1 diabetes mellitus. Phosphorylation of Akt kinase at Thr³⁰⁸ and Ser⁴⁷³ (stimulation) and GSK3β at Ser⁹ (inhibition) was evaluated. In diabetes, phosphorylation of Akt kinase and, to a lesser extent, GSK3β, is reduced. A single injection of insulin or C-peptide and insulin increased this process. Long-term combined treatment with C-peptide and insulin normalized activity of Akt kinase and GSK3β in diabetic rats, treatment with insulin alone produced less pronounced effect; monotherapy with C-peptide was ineffective. Intranasal co-administration of C-peptide and insulin effectively stimulates the insulin system in the hypothalamus that is weakened at diabetes mellitus type 1, which can be used in the treatment of this disease.

Regional-specific effects of cerebral ischemia/reperfusion and dehydroepiandrosterone on synaptic NMDAR/PSD-95 complex in male Wistar rats

Excessive glutamate efflux and N-methyl-D-aspartate receptor (NMDAR) over-activation represent well-known hallmarks of cerebral ischemia/reperfusion (I/R) injury, still, expression of proteins involved in this aspect of I/R pathophysiology show inconsistent data. Neurosteroid dehydroepiandrosterone (DHEA) has been proposed as potent NMDAR modulator, but its influence on I/R-induced changes up to date remains questionable. Therefore, I/R-governed alteration of vesicular glutamate transporter 1 (vGluT1), synaptic NMDAR subunit composition, postsynaptic density protein 95 (PSD-95) and neuronal morphology alone or following DHEA treatment were examined. For that purpose, adult male Wistar rats were treated with a single dose of vehicle or DHEA (20 mg/kg i.p.) 4 h following sham operation or 15 min bilateral common carotid artery occlusion. Western blot was used for analyses of synaptic protein expressions in hippocampus and prefrontal cortex, while neuronal morphology was assessed using Nissl staining. Regional-specific postischemic changes were detected on protein level i.e. signs of neuronal damage in CA1 area was accompanied with hippocampal vGluT1, NR1, NR2B enhancement and PSD-95 decrement, while histological changes observed in layer III were associated with decreased NR1 subunit in prefrontal cortex. Under physiological conditions DHEA had no effect on protein and histological appearance, while in ischemic milieu it restored hippocampal PSD-95 and NR1 in prefrontal cortex to the control level. Along with intact neurons, ones characterized by morphology observed in I/R group were also present. Future studies involving NMDAR-related intracellular signaling and immunohistochemical analysis will reveal precise effects of I/R and DHEA treatment in selected brain regions.

Autophagy and Autophagic Cell Death: Uncovering New Mechanisms Whereby Dehydroepiandrosterone Promotes Beneficial Effects on Human Health

Dehydroepiandrosterone (DHEA) is the most abundant steroid hormone in human serum and a precursor of sexual hormones. Its levels, which are maximum between the age of 20 and 30, dramatically decline with aging thus raising the question that many pathological conditions typical of the elderly might be associated with the decrement of circulating DHEA. Moreover, since its very early discovery, DHEA and its metabolites have been shown to be active in many pathophysiological contexts, including cardiovascular disease, brain disorders, and cancer. Indeed, treatment with DHEA has beneficial effects for the cure of these and many other pathologies in vitro, in vivo, and in patient studies. However, the molecular mechanisms underlying DHEA effects have been only partially elucidated. Autophagy is a self-digestive process, by which cell homeostasis is maintained, damaged organelles removed, and cell survival assured upon stress stimuli. However, high rate of autophagy is detrimental and leads to a form of programmed cell death known as autophagic cell death (ACD). In this chapter, we describe the process of autophagy and the morphological and biochemical features of ACD. Moreover, we analyze the beneficial effects of DHEA in several pathologies and the molecular mechanisms with particular emphasis on its regulation of cell death processes. Finally, we review data indicating DHEA and structurally related steroid hormones as modulators of both autophagy and ACD, a research field that opens new avenues in the therapeutic use of these compounds.

Integrating insulin-like growth factor 1 and sex hormones into neuroprotection: Implications for diabetes

Brain integrity and cognitive aptitude are often impaired in patients with diabetes mellitus, presumably a result of the metabolic complications inherent to the disease. However, an increasing body of evidence has demonstrated the central role of insulin-like growth factor 1 (IGF1) and its relation to sex hormones in many neuroprotective processes. Both male and female patients with diabetes display abnormal IGF1 and sex-hormone levels but the comparison of these fluctuations is seldom a topic of interest. It is interesting to note that both IGF1 and sex hormones have the ability to regulate phosphoinositide 3-kinase-Akt and mitogen-activated protein kinases-extracellular signal-related kinase signaling cascades in animal and cell culture models of neuroprotection. Additionally, there is considerable evidence demonstrating the neuroprotective coupling of IGF1 and estrogen. Androgens have also been implicated in many neuroprotective processes that operate on similar signaling cascades as the estrogen-IGF1 relation. Yet, androgens have not been directly linked to the brain IGF1 system and neuroprotection. Despite the sex-specific variations in brain integrity and hormone levels observed in diabetic patients, the IGF1-sex hormone relation in neuroprotection has yet to be fully substantiated in experimental models of diabetes. Taken together, there is a clear need for the comprehensive analysis of sex differences on brain integrity of diabetic patients and the relationship between IGF1 and sex hormones that may influence brain-health outcomes. As such, this review will briefly outline the basic relation of diabetes and IGF1 and its role in neuroprotection. We will also consider the findings on sex hormones and diabetes as a basis for separately analyzing males and females to identify possible hormone-induced brain abnormalities. Finally, we will introduce the neuroprotective interplay of IGF1 and estrogen and how androgen-derived neuroprotection operates through similar signaling cascades. Future research on both neuroprotection and diabetes should include androgens into the interplay of IGF1 and sex hormones.

Role of DHEA in cardiovascular diseases

Dehydroepiandrosterone (DHEA) is a steroid hormone derived from cholesterol synthesized by the adrenal glands. DHEA and its 3β-sulphate ester (DHEA-S) are the most abundant circulating steroid hormones. In human, there is a clear age-related decline in serum DHEA and DHEA-S and this has suggested that a relative deficiency in these steroids may be causally related to the development of a series of diseases associated with aging including cardiovascular diseases (CVD). This commentary aims to highlight the action of DHEA in CVD and its beneficial effect in therapy. We thus discuss the possible impact of serum DHEA decline and DHEA supplementation in diseases such as hypertension, coronary artery disease and atherosclerosis. More specifically, we provide evidence for a beneficial action of DHEA in the main disease of the pulmonary circulation: pulmonary hypertension. We also examine the potential cellular mechanism of action of DHEA in terms of receptors (membrane/nuclear) and associated signaling pathways (ion channels, calcium signaling, PI3K/AKT/eNos pathway, cGMP, RhoA/RhoK pathway). We show that DHEA acts as an anti-remodeling and vasorelaxant drug. Since it is a well-tolerated and inexpensive drug, DHEA may prove to be a valuable molecule in CVD but it deserves further studies both at the molecular level and in large clinical trials.

DHEA suppresses longitudinal bone growth by acting directly at growth plate through estrogen receptors

Dehydroepiandrosterone (DHEA) is produced by the adrenal cortex and is the most abundant steroid in humans. Although in some physiological and pathological conditions the increased secretion of DHEA and its sulfated form is associated with accelerated growth rate and skeletal maturation, it is unclear whether DHEA can affect longitudinal bone growth and skeletal maturation by acting directly at the growth plate. In our study, DHEA suppressed metatarsal growth, growth plate chondrocyte proliferation, and hypertrophy/differentiation. In addition, DHEA increased the number of apoptotic chondrocytes in the growth plate. In cultured chondrocytes, DHEA reduced chondrocyte proliferation and induced apoptosis. The DHEA-induced inhibition of metatarsal growth and growth plate chondrocyte proliferation and hypertrophy/differentiation was nullified by culturing metatarsals with DHEA in the presence of ICI 182,780, an inhibitor of estrogen receptor, but not in the presence of Casodex, an inhibitor of androgen receptor. Lastly, nuclear factor-κB DNA binding activity was inhibited by the addition of DHEA in the medium of cultured chondrocyte. Our findings indicate that DHEA suppressed bone growth by acting directly at growth plate through estrogen receptor. Such growth inhibition is mediated by decreased chondrocyte proliferation and hypertrophy/differentiation and by increased chondrocyte apoptosis.

Dehydroepiandrosterone effects on Akt signaling modulation in central nervous system of young and aged healthy rats

Dehydroepiandrosterone (DHEA) is a steroid synthesized in adrenal cortex as well as in the nervous system. DHEA effects on central nervous system (CNS) have been associated with several brain functions such as marked neurotrophic and neuroprotective activity. DHEA plasma concentration decreases steadily with aging and studies have reported an inverse correlation between levels of DHEA and neurological diseases age-associated. Nonetheless, its mechanisms of action are not yet fully understood. Akt signaling pathway is one protein kinase which has been related to be DHEA modulated. The goal of this study was to investigate whether short-term (6 or 24h) or chronic (5 weeks) DHEA treatment modulates Akt in CNS of adult (3 months) and aged (18 and 24 months) healthy rats. Hypothalamus and hippocampus homogenates were prepared to quantify total-Akt and phosphorylated Akt at Ser(473) (pAkt). The results here presented have shown that acute (50mg/kg) and chronic (10mg/kg) DHEA injections modulate total and pAkt levels. This effect was dose and time-dependent as well as age and tissue-dependent. In addition, the age variable also intervenes on total and pAkt levels expression independently of DHEA treatment.

Neuroimmunomodulatory steroids in Alzheimer dementia

Though pathobiochemical and neurochemical changes and accompanied morphological alterations in Alzheimer dementia are well known, the triggering mechanisms, if any, remain obscure. Important factors influencing the development and progression of Alzheimer disease include hormonal steroids and their metabolites, some of which may serve as therapeutic agents. This review focusses on major biochemical alterations in the brain of Alzheimer patients with respect to the involvement of steroids. It includes their role in impairment of fuel supply and in brain glycoregulation, with especial emphasis on glucocorticoids and their counter-regulatory steroids as dehydroepiandrosterone and its metabolites. Further, the role of steroids in beta-amyloid pathology is reviewed including alterations in tau-protein(s) phosphorylation. The (auto)immune theory of Alzheimer dementia is briefly outlined, pointing to the possible involvement of steroids in brain ageing, immunosenescence and neuronal apoptosis. Some effects of steroids are briefly mentioned on the formation and removal of reactive oxygen species and their effect on calcium flux and cytotoxicity. The recent biochemical research of Alzheimer disease focusses on molecular signalling at which steroids also take part. New findings may be anticipated when the mosaic describing the molecular mechanisms behind these events becomes more complete.

DHEA-dependent and organ-specific regulation of TNF-alpha mRNA expression in a murine polymicrobial sepsis and trauma model

Introduction

Dehydroepiandrosterone (DHEA) improves survival after trauma and sepsis, while mechanisms of action are not yet fully understood. Therefore, we investigated the influence of DHEA on local cytokine expression in a two-hit model.

Methods

Male NMRI mice were subjected to femur fracture/hemorrhagic shock and subsequent sepsis. Sham-operated animals were used as controls. DHEA (25 mg/kg) or vehicle was administered daily. Mortality rate, activity and body temperature were determined daily after sepsis induction. TNF-α, IL-1β and IL-10 mRNA expression pattern were investigated in lung and liver tissue after 48 and 96 hours.

Results

DHEA treatment resulted in a significantly reduced mortality rate and improvements in the clinical status. On cytokine level, only TNF-α was significantly reduced in the cecal ligation and puncture (CLP)-vehicle group in both tissues after 48 hours. This suppression could be restored by DHEA administration. In contrast, after 96 hours, TNF-α was up-regulated in the CLP-vehicle group while remaining moderate by DHEA treatment in liver tissue.

Conclusions

The improved outcome after DHEA treatment and trauma is coherent with restoration of TNF-α in liver and lung after 48 hours and a counter-regulatory attenuation of TNF-α in liver after 96 hours. Thus, DHEA seems to act, time and organ dependent, as a potent modulator of TNF-α expression.

Variation patterns of two degradation enzyme systems in articular cartilage in different stages of osteoarthritis: regulation by dehydroepiandrosterone

BACKGROUND

Osteoarthritis (OA) is a multifactorial degenerative joint disease in which the cartilaginous matrix of the articular joint is destroyed in a continuous process. We evaluated mRNA levels of cysteine proteinases/cystatin C system and urokinase plasminogen activator/plasminogen activator inhibitor-1 (uPA/PAI-1) system in articular cartilage and regulation by dehydroepiandrosterone (DHEA) in different stages of osteoarthritis (OA).

METHODS

One hundred and eight rabbits underwent anterior cruciate ligament transection (ACLT) in the left knee, 54 received weekly intra-articular injections of DHEA (100 micromol/l) 0.3 ml 3 weeks after transaction as DHEA group. Thirty-six rabbits (18 from 2 groups respectively) were euthanized 6, 9, and 12 weeks after ACLT. All left knee joints were assessed by gross morphology and histology, meantime the gene expression from articular cartilage was analyzed.

RESULTS

Cathepsins and uPA gene increased significantly 6 weeks and reached peak in the 9th week, while declined to extremely low levels 12 weeks after ACLT. Cystatin C decreased accompanied by OA progression, while PAI-1 expressed in the same trend with uPA. Additionally, these 2 enzyme systems were markedly suppressed by DHEA 6 and 9 weeks after ACLT but not in the 12th week.

CONCLUSION

The variation of these 2 enzyme systems was closely related to the progression of OA, and could be regulated by DHEA especially in the early and medium stages of OA.

Activation of the PI3K/Akt pathway early during vaccinia and cowpox virus infections is required for both host survival and viral replication

Viral manipulation of the transduction pathways associated with key cellular functions such as actin remodeling, microtubule stabilization, and survival may favor a productive viral infection. Here we show that consistent with the vaccinia virus (VACV) and cowpox virus (CPXV) requirement for cytoskeleton alterations early during the infection cycle, PBK/Akt was phosphorylated at S473 [Akt(S473-P)], a modification associated with the mammalian target of rapamycin complex 2 (mTORC2), which was paralleled by phosphorylation at T308 [Akt(T308-P)] by PI3K/PDK1, which is required for host survival. Notably, while VACV stimulated Akt(S473-P/T308-P) at early (1 h postinfection [p.i.]) and late (24 h p.i.) times during the infective cycle, CPXV stimulated Akt at early times only. Pharmacological and genetic inhibition of PI3K (LY294002) or Akt (Akt-X and a dominant-negative form of Akt-K179M) resulted in a significant decline in virus yield (from 80% to >/=90%). This decline was secondary to the inhibition of late viral gene expression, which in turn led to an arrest of virion morphogenesis at the immature-virion stage of the viral growth cycle. Furthermore, the cleavage of both caspase-3 and poly(ADP-ribose) polymerase and terminal deoxynucleotidyl transferase-mediated deoxyuridine nick end labeling assays confirmed that permissive, spontaneously immortalized cells such as A31 cells and mouse embryonic fibroblasts (MEFs) underwent apoptosis upon orthopoxvirus infection plus LY294002 treatment. Thus, in A31 cells and MEFs, early viral receptor-mediated signals transmitted via the PI3K/Akt pathway are required and precede the expression of viral antiapoptotic genes. Additionally, the inhibition of these signals resulted in the apoptosis of the infected cells and a significant decline in viral titers.

Gamma-aminobutyric acid nurtures allergic asthma

Asthma often occurs as a result of immune-based inflammatory responses, which consequently cause pathological changes in airway structural cells. However, the underlying mechanisms of airway pathology in asthma are still not fully understood. Our recent studies revealed a critical role of gamma-aminobutyric acid (GABA) signalling pathway in the airway epithelium of allergic asthma through its ability to stimulate mucus production. This review briefly describes the GABAergic signalling system and its role in the regulation of mucus protein production in bronchial airway epithelial cells.

DHEA-neuroprotection and -neurotoxicity after transient cerebral ischemia in rats

Dehydroepiandrosterone (DHEA) has been implicated not only to prevent N-methyl-D-aspartate (NMDA)-induced neurotoxicity but also to enhance Ca(2+) influx through NMDA receptor (NMDAr). However, these DHEA effects, which would produce inconsistent outcomes about neuronal damages, are not well studied in ischemia-induced cerebral damages. Herein, we report that a single administration of DHEA (20 mg/kg) during 3 to 48 h after transient global cerebral ischemia in rats exerted neuroprotective effects such as reduction of ischemia-induced neuronal death in the hippocampal CA1 and improvement of ischemia-induced deficits in spatial learning. By contrast, at 1 h before or after ischemia, the administration of DHEA exacerbated the ischemia-induced neuronal death and learning impairment. This DHEA neurotoxicity appeared to be caused by DHEA itself, but not through its metabolite testosterone, and was inhibited by a pretreatment with the NMDAr blocker MK801 or the sigma-1 (sigma(1)) receptor antagonist NE100. However, the DHEA neuroprotection was blocked by NE100. These results show that DHEA not only provides robust ischemic neuroprotection with a long therapeutic opportunity but also exerts neurotoxicity when administered during ischemia and early reperfusion, which points to the importance of administration timing of DHEA in the clinical treatment of brain damages by the transient brain ischemia including stroke.

Neurosteroid dehydroepiandrosterone exerts anti-apoptotic effects by membrane-mediated, integrated genomic and non-genomic pro-survival signaling pathways

Dehydroepiandrosterone (DHEA) protects neural crest-derived PC12 cells from serum deprivation-induced apoptosis via G protein-associated specific plasma membrane-binding sites (mDBS). Here, we studied the signaling pathways involved in the pro-survival effects of DHEA-mediated activation of the mDBS binding sites. Membrane impermeable DHEA-bovine serum albumin (BSA) conjugate induced an acute phosphorylation of the prosurvival kinases Src, protein kinase A (PKA), MEK1/2/ERK1/2, and PI3K/Akt in serum deprived PC12 cells in parallel to an elevation of intracellular cAMP. The physiological significance of these findings was further assessed in a series of experiments using several selective pro-survival kinase inhibitors. Our combined findings suggest that the following sequence of events may take place following activation of mDBS binding sites: DHEA-BSA induces an acute but transient sequential phosphorylation of the pro-survival kinases Src/PKC(a/b)/MEK1/2/ERK1/2 which, in their turn, activate transcription factors cAMP responsive element binding protein and nuclear factor kappa B which induce the expression of the anti-apoptotic Bcl-2 genes. In parallel, DHEA-BSA increases intracellular cAMP, and the subsequent phosphorylation of PKA kinase and of cAMP responsive element binding protein. Finally, DHEA-BSA induces phosphorylation of PI3K/Akt kinases which, subsequently, lead to phosphorylation/deactivation of the pro-apoptotic Bad. Our findings suggest that the neurosteroid DHEA affects neural crest-derived cell survival by multiple pro-survival signaling pathways comprising an integrated system of non-genomic and genomic mechanisms.

Involvement of the PI3K/Akt pathway in estrogen-mediated regulation of human CYP7B1: identification of CYP7B1 as a novel target for PI3K/Akt and MAPK signalling

The steroid hydroxylase CYP7B1 metabolizes neurosteroids, cholesterol derivatives, and estrogen receptor (ER) ligands. Previous studies identified CYP7B1 as a target for regulation by estrogen. The present study examines the mechanism for estrogen-mediated regulation of the human CYP7B1 gene promoter. Treatment with LY294002, a specific inhibitor of phosphatidylinositol 3-kinase (PI3K), abolished ER-mediated up-regulation of a CYP7B1 promoter-luciferase reporter in HepG2 cells, whereas overexpression of PI3K or Akt significantly increased estrogenic up-regulation of CYP7B1. Overexpression of dominant-negative mutant Akt abolished ER-mediated stimulation of CYP7B1 in HepG2 cells. Data indicated no binding of ER to CYP7B1 promoter sequences, suggesting that ER interacts with the PI3K/Akt pathway without binding to the gene. At low ER levels, overexpression of Akt suppressed CYP7B1 promoter activity, suggesting that its effect on CYP7B1 is different when estrogens are absent. In HEK293 cells, CYP7B1 transcription was much less affected by Akt, indicating that the mechanism for up-regulation of CYP7B1 is different in different cell types. Other experiments indicated that MAPK signalling may affect basal CYP7B1 levels. The current results, indicating that regulation of CYP7B1 by ER can be mediated via the PI3K/Akt signal pathway, a regulatory pathway important for cellular survival and growth, suggest an important role for CYP7B1 in cellular growth, particularly in connection with estrogenic signalling.

Expression profile of human cells in culture exposed to glycidamide, a reactive metabolite of the heat-induced food carcinogen acrylamide

Recent findings of acrylamide in many common foods have sparked renewed interest in assessing human health hazards and the long-term risk associated with exposure to vinyl compounds. Acrylamide is tumorigenic at high doses in rodents and has been classified as a probable human carcinogen. However, cancer risk projections in the population remain problematic because the molecular pathogenesis of acrylamide at the low level of dietary uptake is not understood. In particular, the question of whether specific transcriptional responses may amplify or mitigate the known genotoxicity of acrylamide has never been examined. Here, we used high-density DNA microarrays and PCR validations to assess genome-wide messenger profiles induced by glycidamide, the more reactive metabolite of acrylamide. The expression changes resulting from glycidamide treatment of human epithelial cells are characterized by the induction of detoxification enzymes, several members of the glutathione system and antioxidant factors. Low-dose experiments indicate that the up-regulation of epoxide hydrolase 1 represents the most sensitive transcriptional biomarker of glycidamide exposure. At higher concentrations, glycidamide induces typical markers of tumor progression such as steroid hormone activators, positive regulators of nuclear factor-kappaB, growth stimulators and apoptosis inhibitors. Concomitantly, growth suppressors and cell adhesion molecules are down-regulated. The main implication of these findings for risk assessment is that low concentrations of glycidamide elicit cytoprotective reactions whereas transcriptional signatures associated with tumor progression may be expected only at doses that exceed the range of ordinary dietary exposures.

Dominant role of betagamma subunits of G-proteins in oxytocin-evoked burst firing

Pulsatile neuropeptide secretion is associated with burst firing patterns; however, intracellular signaling cascades leading to bursts remain unclear. We explored mechanisms underlying burst firing in oxytocin (OT) neurons in the supraoptic nucleus in brain slices from lactating rats. Application of 10 pm OT for 30 min or progressively rising OT concentrations from 1 to 100 pm induced burst firing in OT neurons in patch-clamp recordings. Burst generation was blocked by OT antagonist and ionotropic glutamate receptor blockers or tetanus toxin. Blocking G-protein activation with suramin or intracellular GDP-beta-S, but not intracellularly administered antibody against the OT-receptor (OTR) C terminus, blocked bursts. Moreover, pretreatment of slices with pertussis toxin, an inhibitor of G(i/o)-proteins, did not block OT-evoked bursts, suggesting that G(i)/G(o) activation is unnecessary for burst generation. Thus, we further examined G alpha(q/11)-associated signaling pathways in OT-evoked bursts. Inhibition of phospholipase C or RhoA/Rho kinase did not block bursts. Activation of G betagamma subunits using myristoylated G betagamma-binding peptide (mSIRK) caused bursts, whereas intracellularly loaded antibody against G beta subunit blocked OT-evoked bursts. Blocking Src family kinase, but not phosphatidylinositol 3-kinase, occluded OT-evoked bursts. Similar to the effects of OT on EPSCs, mSIRK inhibited tonic EPSCs and elicited EPSC clustering. Finally, suckling caused dissociation of OTRs and G beta subunits from G alpha(q/11) subunits shown by coimmunoprecipitation and immunocytochemistry, supporting crucial roles for OTRs and G betagamma subunits in the milk-ejection reflex. We conclude that G betagamma subunits play a dominant role in burst firing evoked by applied OT or by suckling.

Dehydroepiandrosterone administration modulates endothelial and neutrophil adhesion molecule expression in vitro

Introduction

The steroid hormone dehydroepiandrosterone (DHEA) exerts protecting effects in the treatment of traumatic and septic complications in several animal models. This effect goes along with reduced amounts of infiltrating immune cells in organs such as lung and liver. However, the underlying mechanisms of DHEA action are still not known. Adhesion molecules are important for the extravasation of neutrophils into organs where they may exhibit detrimental effects. Therefore, we investigated the in vitro effect of DHEA on the expression pattern of adhesion molecules of human endothelial cells and neutrophils.

Methods

Endothelial cells derived from human umbilical cord were subjected to an lipopolysaccharide (LPS) challenge. DHEA was administered in two different concentrations, 10^-5 M and 10^-8 M, as a single stimulus or in combination with LPS challenge. After two, four and 24 hours, fluorescence activated cell sorter (FACS) analysis for vascular cell adhesion molecule-1, intercellular adhesion molecule-1 and E-selectin was performed. Neutrophils were freshly isolated from blood of 10 male healthy volunteers, stimulated the same way as endothelial cells and analyzed for surface expression of L-selectin, CD11b and CD18.

Results

In the present study, we were able to demonstrate effects of DHEA on the expression of every adhesion molecule investigated. DHEA exhibits opposite effects to those seen upon LPS exposure. Furthermore, these effects are both time and concentration dependent as most DHEA specific effects could be detected in the physiological concentration of 10^-8 M.

Conclusion

Thus, we conclude that one mechanism by which DHEA may exert its protection in animal models is via the differential regulation of adhesion molecule expression.

Melanocortin-4 receptor-mediated inhibition of apoptosis in immortalized hypothalamic neurons via mitogen-activated protein kinase

The melanocortin-4 receptor (MC4R) is a seven transmembrane member of the melanocortin receptor family. The GT1-1 cell line exhibits endogenous expression of MC4R. In this study, GT1-1 cells were used to study MC4R signaling pathways and to examine the effects of melanocortin receptor agonist NDP-MSH on apoptosis. MC4R mRNA expression was demonstrated by RT-PCR. Functional melanocortin receptor expression was implied by specific binding of NDP-MSH and cAMP production. NDP-MSH-stimulated GnRH release in a dose-dependent manner. Serum deprivation-induced apoptosis in GT1-1 cells, and the NDP-MSH inhibited this effect. The melanocortin receptor antagonist SHU9119 blocked the antiapoptotic actions of NDP-MSH, and the MAP kinase inhibitor PD98059 significantly attenuated the antiapoptotic effect. NDP-MSH-stimulated ERK1/2 phosphorylation in a dose-dependent manner. ERK1/2 phosphorylation could be abolished by SHU9119. In GT1-1 cells, melanocortin receptor activation causes ERK1/2 phosphorylation. In these cells, MC4R activation is also associated with antiapoptotic effects.

Neuroprotective strategies for HIV-1 associated dementia

The human immunodeficiency virus-1 (HIV-1) commonly affects cognitive, behavioral and motor functions during the disease course. The neuropathogenesis of viral infection revolves around neurotoxins produced from infected and immune-activated mononuclear phagocytes (MP; perivascular macrophages and microglia). Direct infection of neurons occurs rarely, if at all. Neurologic disease arises in part as a consequence of MP metabolic dysfunction. Although the advent of highly active antiretroviral therapy (HAART) has attenuated the incidence and severity of neurologic disease, it, nonetheless, remains a common and disabling problem for those living with HIV-1 infection. Adjunctive therapies are currently designed to ameliorate clinical outcomes and are included in the therapeutic armamentarium. Anti-inflammatory drugs that inhibit cytokines, chemokines and interferons linked to neurodegenerative processes can significantly ameliorate neuronal function. HIV-1 neurotoxins have the unique ability to up-regulate glycogen synthase kinase-3beta (GSK-3beta) activity that in turn elicits neuronal apoptosis. GSK-3beta inhibitors are neuroprotective in animal models of Neuro AIDS. They are also currently in Phase 1 clinical trials designed for safety and tolerability in patients with HIV-1 infection. Neurotrophins are only beginning to be realized for their therapeutic potential in HIV-1 associated neurologic disease. This review article provides a broad overview of neuroprotective strategies for HIV-1 infection and details how such strategies act and may be implemented for treatment of human disease.